Dear EarthTalk: If the ice caps are melting, what is happening to the salt content of the oceans? And might this contribute to weather patterns or cause other environmental problems?

—George Boyer, via e-mail

It’s true that the melting of the polar ice caps as a result of global warming is sending large amounts of freshwater into the world’s oceans. Environmentalists and many climate scientists fear that if the climate heats up fast enough and melts off the remaining polar ice rapidly, the influx of freshwater could disturb ocean currents enough to drastically change the weather on the land as well.

The Gulf Stream, a ribbon of ocean water that delivers heat from the tropics up to the North Atlantic, keeps northeastern U.S. and northwestern Europe weather much milder than other areas at the same latitude around the globe. In theory, less salt in the ocean could stall out the Gulf Stream and rob some of the world’s greatest civilization centers of their natural heating source, plunging the two continents into a cold snap that could last decades or longer—even as the rest of the globe warms around them.

The Gulf Stream keeps running because the warmer water travelling north is lighter than cold water, so it floats on top and keeps moving. As the current approaches the northern Atlantic and disgorges its heat, it grows denser and sinks, at which point it flows back to the south, crossing under the northbound Gulf Stream, until it reaches the tropics to start the cycle all over again. This cycle has allowed humans and other life forms to thrive across wide swaths of formerly frozen continents over thousands of years. But if too much dilution occurs, the water will get lighter, idling on top and stalling out the system.

Some scientists worry that this grim future is fast approaching. Researchers from Britain’s National Oceanography Center have noticed a marked slowing in the Gulf Stream since the late 1950s. They suspect that the increased release of Arctic and Greenland meltwater is to blame for overwhelming the cycle, and fear that more warming could plunge temperatures significantly lower across land masses known as some of the most hospitable places for humans to live.

Of course—not surprisingly—others have noted a contradictory trend: Some parts of the world’s oceans are getting saltier. Researchers from the UK’s Met Office and Reading University reported in a recent issue of the peer-reviewed journal Geophysical Research Letters that warmer temperatures over southerly sections of the Atlantic Ocean have significantly increased evaporation and reduced rainfall from Africa to the Caribbean in recent years, concentrating salt in the water that’s left behind. In fact, the Atlantic in this region is about 0.5 percent saltier than it was four decades ago.

But given how little we really know about the future effects of our carbon loading of the atmosphere, calling these two trends contradictory might be premature—as the two regions of ocean interact with one another and are part of a larger whole. Looking instead at the big picture, it’s clear that climate change is already having a relatively large effect on the world’s oceans by fundamentally altering evaporation and precipitation cycles. Only time will tell how dramatic the results of these changes will be.

Americans recycle more plastic than ever these days, but there are still plenty of items that are not accepted by municipalities, including many hard plastic items like ski boots.

If such items are still usable, consider donating them to a local Goodwill or Salvation Army store, which can sell them and put the money earned toward housing and feeding those less fortunate. Another option would be to sell or give them to a second-hand sporting goods store, which might even give you trade-in credit toward an upgrade. If you can’t find somewhere local, you can ship them to Colorado-based Boulder Ski Deals. The company accepts ski boots (along with skis, bindings, poles and snowboards) for recycling, donating usable equipment to charitable programs and shredding the rest for re-use in making new products.

The fact that it is so difficult to recycle hard plastic items is a growing issue as we all try to minimize our impact on the environment. Everyone involved with the lifecycle of a given item—from manufacturer to retailer to consumer—can share the blame when something ends up taking up precious space in a landfill instead of being recycled in one way or another. Concerned consumers should make sure that a given item is easy to recycle when its usefulness runs its course before buying it in the first place. It also can’t hurt to let a manufacturer know that you didn’t purchase a given product because it didn’t meet your recyclability standards. Manufacturers want to make products that people will buy and such feedback can go a long way to getting them to re-think their practices.

Likewise, municipalities need to hear from residents if there is a need to expand the types of items accepted for recycling. If enough people are willing to recycle a certain type of item, it may be worthwhile for the municipality to expand capacity and move into new markets.

The good news is that there are plenty of firms that are happy to take back otherwise difficult-to-recycle stuff. The non-profit Earth911 offers up a free searchable online database of different types of recyclers keyed to the user’s zip code anywhere across the United States. If no local provider comes up, the site will refer users to a place that accepts shipped items. Another good resource is the consulting firm Eco-Officiency’s concise yet comprehensive online list of companies around the country that accept different types of hard plastic and other hard-to-recycle items.

Consumers should keep in mind that they may have to pay for the privilege of recycling certain items, as well as shipping costs. If you can swing it, think of it as a tax for buying something less friendly to the environment. Maybe next time you"ll look for one made out of easier-to-recycle materials.

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